Staff Publications

Staff Publications

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    'Staff publications' is the digital repository of Wageningen University & Research

    'Staff publications' contains references to publications authored by Wageningen University staff from 1976 onward.

    Publications authored by the staff of the Research Institutes are available from 1995 onwards.

    Full text documents are added when available. The database is updated daily and currently holds about 240,000 items, of which 72,000 in open access.

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    Lactate formation and subsequent chain elongation in repeated-batch food waste fermentation
    Contreras Davila, Carlos ; Carrión, Víctor J. ; Vonk, Vincent R. ; Buisman, Cees ; Strik, David - \ 2020
    Wageningen University & Research
    PRJEB33791 - ERP116611 - metagenome - lactate - n-caproate - food waste - fermentation
    The production of biochemicals, materials and biofuels from renewables through biorefinery processes is important to reduce the anthropogenic impact on the environment. Chain elongation processes based on open microbiomes have been successfully developed to produce medium-chain fatty acids (versatile platform products) from organic waste streams. Yet, the sustainability of chain elongation can still be improved by reducing the use of electron donors and reducing chemicals use. This work aimed to in situ produce the electron donor lactate coupled to subsequent chain elongation for n-caproate production with decreased chemicals use for pH control. Food waste was used as substrate in repeated-batch fermentation experiments.
    Microbial Engineering for Production of N-Functionalized Amino Acids and Amines
    Mindt, Melanie ; Walter, Tatjana ; Kugler, Pierre ; Wendisch, Volker F. - \ 2020
    Biotechnology Journal (2020). - ISSN 1860-6768
    bioactives - fermentation - metabolic engineering - N-functionalization - natural products

    N-functionalized amines play important roles in nature and occur, for example, in the antibiotic vancomycin, the immunosuppressant cyclosporine, the cytostatic actinomycin, the siderophore aerobactin, the cyanogenic glucoside linamarin, and the polyamine spermidine. In the pharmaceutical and fine-chemical industries N-functionalized amines are used as building blocks for the preparation of bioactive molecules. Processes based on fermentation and on enzyme catalysis have been developed to provide sustainable manufacturing routes to N-alkylated, N-hydroxylated, N-acylated, or other N-functionalized amines including polyamines. Metabolic engineering for provision of precursor metabolites is combined with heterologous N-functionalizing enzymes such as imine or ketimine reductases, opine or amino acid dehydrogenases, N-hydroxylases, N-acyltransferase, or polyamine synthetases. Recent progress and applications of fermentative processes using metabolically engineered bacteria and yeasts along with the employed enzymes are reviewed and the perspectives on developing new fermentative processes based on insight from enzyme catalysis are discussed.

    Gastrointestinal Bioaccessibility and Colonic Fermentation of Fucoxanthin from the Extract of the Microalga Nitzschia laevis
    Guo, Bingbing ; Oliviero, Teresa ; Fogliano, Vincenzo ; Ma, Yuwei ; Chen, Feng ; Capuano, Edoardo - \ 2020
    Journal of Agricultural and Food Chemistry 68 (2020)7. - ISSN 0021-8561 - p. 1844 - 1850.
    digestion - fermentation - fucoxanthin - microalgae

    The extract of microalga Nitzschia laevis (NLE) is considered a source of dietary fucoxanthin, a carotenoid possessing a variety of health benefits. In the present study, the bioaccessibility and deacetylation of fucoxanthin were studied by simulated in vitro gastrointestinal digestion and colonic batch fermentation. In the gastric phase, higher fucoxanthin loss was observed at pH 3 compared to pH 4 and 5. Lipases are crucial for the deacetylation of fucoxanthin into fucoxanthinol. Fucoxanthinol production decreased significantly in the order: pure fucoxanthin (25.3%) > NLE (21.3%) > fucoxanthin-containing emulsion (11.74%). More than 32.7% of fucoxanthin and fucoxanthinol was bioaccessible after gastrointestinal digestion of NLE. During colon fermentation of NLE, a higher loss of fucoxanthin and changes of short-chain fatty acid production were observed but no fucoxanthinol was detected. Altogether, we provided novel insights on the fucoxanthin fate along the human digestion tract and showed the potential of NLE as a promising source of fucoxanthin.

    Review: Rumen sensors: Data and interpretation for key rumen metabolic processes
    Dijkstra, J. ; Gastelen, S. Van; Dieho, K. ; Nichols, K. ; Bannink, A. - \ 2020
    Animal 14 (2020)S1. - ISSN 1751-7311 - p. S176 - S186.
    data analysis - diurnal variation - fermentation - ruminants

    Rumen sensors provide specific information to help understand rumen functioning in relation to health disorders and to assist in decision-making for farm management. This review focuses on the use of rumen sensors to measure ruminal pH and discusses variation in pH in both time and location, pH-associated disorders and data analysis methods to summarize and interpret rumen pH data. Discussion on the use of rumen sensors to measure redox potential as an indication of the fermentation processes is also included. Acids may accumulate and reduce ruminal pH if acid removal from the rumen and rumen buffering cannot keep pace with their production. The complexity of the factors involved, combined with the interactions between the rumen and the host that ultimately determine ruminal pH, results in large variation among animals in their pH response to dietary or other changes. Although ruminal pH and pH dynamics only partially explain the typical symptoms of acidosis, it remains a main indicator and may assist to optimize rumen function. Rumen pH sensors allow continuous monitoring of pH and of diurnal variation in pH in individual animals. Substantial drift of non-retrievable rumen pH sensors, and the difficulty to calibrate these sensors, limits their application. Significant within-day variation in ruminal pH is frequently observed, and large distinct differences in pH between locations in the rumen occur. The magnitude of pH differences between locations appears to be diet dependent. Universal application of fixed conversion factors to correct for absolute pH differences between locations should be avoided. Rumen sensors provide high-resolution kinetics of pH and a vast amount of data. Commonly reported pH characteristics include mean and minimum pH, but these do not properly reflect severity of pH depression. The area under the pH × time curve integrates both duration and extent of pH depression. The use of this characteristic, as well as summarizing parameters obtained from fitting equations to cumulative pH data, is recommended to identify pH variation in relation to acidosis. Some rumen sensors can also measure the redox potential. This measurement helps to understand rumen functioning, as the redox potential of rumen fluid directly reflects the microbial intracellular redox balance status and impacts fermentative activity of rumen microorganisms. Taken together, proper assessment and interpretation of data generated by rumen sensors requires consideration of their limitations under various conditions.

    Fermentations great promise
    Smid, E.J. - \ 2019
    biobased economy - microorganisms - bacteria - chemicals - food - fatty acids - kerosene - fermentation
    Efficient succinic acid production from high-sugar-content beverages by Actinobacillus succinogenes
    Ferone, Mariateresa ; Ercole, Alessia ; Raganati, Francesca ; Olivieri, Giuseppe ; Salatino, Piero ; Marzocchella, Antonio - \ 2019
    Biotechnology Progress 35 (2019)5. - ISSN 8756-7938
    Actinobacillus succinogenes - biorefinery - fermentation - high-content-sugar beverages - succinic acid

    This study presents the production of succinic acid (SA) by Actinobacillus succinogenes using high-sugar-content beverages (HSCBs) as feedstock. The aim of this study was the valorization of a by-product stream from the beverage industry for the production of an important building block chemical, such as SA. Three types of commercial beverages were investigated: fruit juices (pineapple and ace), syrups (almond), and soft drinks (cola and lemon). They contained mainly glucose, fructose, and sucrose at high concentration—between 50 and 1,000 g/L. The batch fermentation tests highlighted that A. succinogenes was able to grow on HSCBs supplemented with yeast extract, but also on the unsupplemented fruit juices. Indeed, the bacteria did not grow on the unsupplemented syrup and soft drinks because of the lack of indispensable nutrients. About 30–40 g/L of SA were obtained, depending on the type of HSCB, with yield ranging between 0.75 and 1.00 gSA/gS. The prehydrolysis step improved the fermentation performance: SA production was improved by 6–24%, depending on the HSCB, and sugar conversion was improved of about 30–50%.

    Data from: Robust sampling and preservation of DNA for microbial community profiling in field experiments
    Groenenboom, A.E. - \ 2019
    DNA stabilisation - fermentation - field trial - filter paper disks - microbial community - milk
    This dataset provides the fasta files of all 83 samples from the clone library as well as the firts result of the BLAST analyses in NCBI database. Also it provides the raw reads of the sequencing in the 16S rRNA region. A meta data file indicates for both analyses methods the type of sample (liquid or paper) the origin of the sampels and the name in the corresponding sequencing files
    Bioreactors for succinic acid production processes
    Ferone, Mariateresa ; Raganati, Francesca ; Olivieri, Giuseppe ; Marzocchella, Antonio - \ 2019
    Critical Reviews in Biotechnology 39 (2019)4. - ISSN 0738-8551 - p. 571 - 586.
    batch and continuous process - bioreactor - biorefinery - fermentation - Succinic acid

    Succinic acid (SA) has been recognized as one of the most important bio-based building block chemicals due to its numerous potential applications. Fermentation SA production from renewable carbohydrate feedstocks can have the economic and sustainability potential to replace petroleum-based production in the future, not only for existing markets, but also for new larger volume markets. Design and operation of bio-reactors play a key role. During the last 20 years, many different fermentation strategies for SA production have been described in literature, including utilization of immobilized biocatalysts, integrated fermentation and separation systems and batch, fed-batch, and continuous operation modes. This review is an overview of different fermentation process design developed over the past decade and provides a perspective on remaining challenges for an economically feasible succinate production processes. The analysis stresses the idea of improving the efficiency of the fermentation stage by improving bioreactor design and by increasing bioreactor performance.

    Trichococcus shcherbakoviae sp. nov., isolated from a laboratory-scale anaerobic EGSB bioreactor operated at low temperature
    Parshina, Sofiya Nikolaevna ; Strepis, Nikolaos ; Aalvink, Steven ; Nozhevnikova, Alla N. ; Stams, Alfons J.M. ; Sousa, Diana Z. - \ 2019
    International Journal of Systematic and Evolutionary Microbiology 69 (2019)2. - ISSN 1466-5026 - p. 529 - 534.
    anaerobic bioreactor - digital DNA–DNA hybridization - fermentation - psychrotolerant - Trichococcus shcherbakoviae

    A new species of the genus Trichococcus, strain Art1T, was isolated from a psychrotolerant syntrophic propionate-oxidizing consortium, obtained before from a low-temperature EGSB reactor fed with a mixture of VFAs (acetate, propionate and butyrate). The 16S rRNA gene sequence of strain Art1T was highly similar to those of other Trichococcus species (99.7-99.9 %) but digital DNA-DNA hybridization values were lower than those recommended for the delineation of a novel species, indicating that strain Art1T is a novel species of the genus Trichococcus. Cells of strain Art1T are non-motile cocci with a diameter of 0.5-2.0 µm and were observed singularly, in pairs, short chains and irregular conglomerates. Cells of Art1T stained Gram-positive and produced extracellular polymeric substances . Growth was optimal at pH 6-7.5 and cells could grow in a temperature range of from -2 to 30 °C (optimum 25-30 °C). Strain Art1T can degrade several carbohydrates, and the main products from glucose fermentation are lactate, acetate, formate and ethanol. The genomic DNA G+C content of strain Art1T is 46.7 %. The major components of the cellular fatty acids are C16 : 1 ω9c, C16 : 0 and C18 : 1 ω9c. Based on genomic and physiological characteristics of strain Art1T, a new species of the genus Trichococcus, Trichococcusshcherbakoviae, is proposed. The type strain of Trichococcusshcherbakoviae is Art1T (=DSM 107162T = VKM B-3260T).

    Application of apigeninidin-rich red sorghum biocolorant in a fermented food improves product quality
    Akogou, Folachodé U.G. ; Canoy, Tessa S. ; Kayodé, Adéchola P.P. ; Besten, Heidy M.W. den; Linnemann, Anita R. ; Fogliano, Vincenzo - \ 2019
    Journal of the Science of Food and Agriculture 99 (2019)4. - ISSN 0022-5142 - p. 2014 - 2020.
    antioxidant activity - apigeninidin - fermentation - maize dough - nutritional quality - volatile compounds

    BACKGROUND: The ‘clean label’ trend is pushing the food industry to replace synthetic colorants with plant-based colorants. However, technological efficacy and undesirable side effects restrict the use of plant-based colorants in industrial applications. This research studied the production of fermented maize dough coloured by apigeninidin-rich red sorghum biocolorant, as practised for centuries in West Africa, as a model to assess the impact of the biocolorant on nutritional and sensorial quality of foods. RESULTS: A 3-day fermentation of a dyed maize dough (containing 327 µg g−1 dry matter of apigeninidin) by Pichia kudriavzevii and Lactobacillus fermentum led to a degradation of 69% of the apigeninidin content, causing a clearly visible colour difference (ΔE*00 17.4). The antioxidant activity of fermented dyed dough (DD) increased by 51% compared to fermented non-dyed dough (NDD). However, the phytate dephosphorylation and volatile organic compound concentrations were lower in DD than in NDD. This suggests a lower mineral solubility and change in the sensory quality of fermented DD. CONCLUSION: Apigeninidin extract from sorghum leaf sheaths proved to be a bioactive red biocolorant with potential in fermented foods. The formation of new antioxidant compounds needs further investigation, as does the impact on the development of volatile compounds.

    Final report: Environmental assessment of algae-based PUFA production
    Keller, H. ; Reinhardt, G. ; Rettenmaier, N. ; Schorb, A. ; Dittrich, M. ; Wolf, P.L. de; Voort, M.P.J. van der; Spruijt, J. ; Potters, J.I. ; Elissen, H.J.H. - \ 2017
    Heidelberg : PUFAChain - 94
    algae - biofuels - bioenergy - biobased economy - biomass - omega-3 fatty acids - plant oils - biobased chemistry - fermentation
    Fermentatie is hot: nieuwe toepassingen van een oeroude techniek
    Smid, E.J. ; Hugenholtz, J. - \ 2017
    biofuels - biobased economy - bioenergy - chemical industry - nutrition - fermentation - cellulose - bacteria - biomass
    Predicting methane emission of dairy cows using milk composition
    Gastelen, Sanne van - \ 2017
    Wageningen University. Promotor(en): W.H. Hendriks, co-promotor(en): J. Dijkstra; K.A. Hettinga. - Wageningen : Wageningen University - ISBN 9789463437097 - 266
    dairy cows - dairy cattle - methane production - emission - milk composition - fatty acids - cattle feeding - fermentation - nutrition physiology - animal nutrition - pollution - melkkoeien - melkvee - methaanproductie - emissie - melksamenstelling - vetzuren - rundveevoeding - fermentatie - voedingsfysiologie - diervoeding - verontreiniging

    Enteric methane (CH4) is produced as a result of microbial fermentation of feed components in the gastrointestinal tract of ruminant livestock. Methane has no nutritional value for the animal and is predominately released into the environment through eructation and breath. Therefore, CH4 not only represents a greenhouse gas contributing to global warming, but also an energy loss, making enteric CH4 production one of the main targets of greenhouse gas mitigation practices for the dairy industry. Obviously, reduction of CH4 emission could be achieved by simply reducing livestock numbers. However, the global demand for dairy products has been growing rapidly and is expected to further grow in the future. Therefore, it is critical to minimize environmental impact to produce high-quality dairy products. The overall aim of this PhD research was, therefore, to develop a proxy for CH4 emission that can be measured in milk of dairy cows.

    There are currently a number of potentially effective dietary CH4 mitigation practices available for the livestock sector. The results of Chapter 3 show that replacing fiber-rich grass silage with starch-rich corn silage in a common forage-based diet for dairy cattle offers an effective strategy to decrease enteric CH4 production without negatively affecting dairy cow performance, although a critical level of starch in the diet seems to be needed. Little is known whether host genetics may influence the CH4 emission response to changes in diet. Therefore, the interaction between host DGAT1 K232A polymorphism with dietary linseed oil supplementation was evaluated in Chapter 7. The results of Chapter 7 indicate that DGAT1 K232A polymorphism is associated with changes in milk composition, milk N efficiency, and diet metabolizability, but does not affect digestibility and enteric CH4 emission, whereas linseed oil reduces CH4 emission independent of the DGAT1 K232A polymorphism.

    Accurate and repeatable measurements of CH4 emission from individual dairy cows are required to assess the efficacy of possible mitigation strategies. There are several techniques to estimate or measure enteric CH4 production of dairy cows, including climate respiration chambers, but none of these techniques are suitable for large scale precise and accurate measurements. Therefore, the potential of various metabolites in milk, including milk fatty acids (MFA), as a proxy (i.e., indicators or animal traits that are correlated with enteric CH4 production) for CH4 emission of dairy cows gained interest. Until recently, gas chromatography was the principal method used to determine the MFA profile, but this technique is unsuitable for routine analysis. This has led to the application of Fourier-transform infrared spectroscopy (FTIR) for determination of the MFA profile. Chapter 2 provides an overview of the recent research that relates MFA with CH4 emission, and discusses the opportunities and limitations of using FTIR to estimate, indirectly via MFA or directly, CH4 emission of dairy cattle. The recent literature on the relationship between MFA and CH4 emission gives inconsistent results. Where some studies found a clear and strong relation, other studies consider MFA to be unreliable predictors for CH4 emitted by dairy cows. Even the studies that do find a clear relation between MFA and CH4 emissions do not describe similar prediction models using the same MFA. These discrepancies can be the result of many factors, including dietary composition and lactation stage. Additionally, literature showed that the major advantages of using FTIR to predict CH4 emission include its simplicity and potential practical application on a large scale. Disadvantages include the inability to predict important MFA for the prediction of CH4 emission, and the moderate power of FTIR to directly predict CH4 emission. The latter was also demonstrated in Chapter 9, in which the CH4 prediction potential of MFA was compared with that of FTIR using data from 9 experiments (n = 218 individual cow observations) covering a broad range of roughage-based diets. The results indicate that MFA have a greater potential than FTIR spectra to estimate CH4 emissions, and that both techniques have potential to predict CH4 emission of dairy cows, but also limited current applicability in practice. Much focus has been placed on the relationship between MFA and CH4 emission, but milk also contains other metabolites, such as volatile and non-volatile metabolites. Currently, milk volatile metabolites have been used for tracing animal feeding systems and milk non-volatile metabolites were shown to be related to the health status of cows. In Chapter 4, the relationship between CH4 emission and both volatile and non-volatile metabolites was investigated, using data and milk samples obtained in the study described in Chapter 3. In general, the non-volatile metabolites were more closely related to CH4 emissions than the volatile metabolites. More specifically, the results indicate that CH4 intensity (g/kg fat- and protein-corrected milk; FPCM) may be related to lactose synthesis and energy metabolism in the mammary gland, as reflected by the milk non-volatile metabolites uridine diphosphate-hexose B and citrate. Methane yield (g/kg dry matter intake) on the other hand, may be related to glucogenic nutrient supply, as reflected by the milk non-volatile acetone. Based on the metabolic interpretations of these relationships, it was hypothesized that the addition of both volatile and non-volatile metabolites in a prediction model with only MFA would enhance its predictive power and, thus, leads to a better proxy in milk for enteric CH4 production of dairy cows. This was investigated in Chapter 5, again using data and milk samples described in Chapter 3. The results indicate that MFA alone have moderate to good potential to estimate CH4 emission. Furthermore, including volatile metabolites (CH4 intensity only) and non-volatile metabolites increases the CH4 emission prediction potential.

    The work presented in Chapters 3, 4 and 5, was based upon a small range of diets (i.e., four roughage-based diets in which grass silage was replaced partly or fully by corn silage) of one experiment. Therefore, in Chapter 6, the relationship between CH4 emission and the milk metabolome in dairy cattle was further quantified. Data (n = 123 individual cow observations) were used encompassing a large of roughage-based diets, with different qualities and proportions of grass, grass silage and corn silage. The results show that changes in individual milk metabolite concentrations can be related to the ruminal CH4 production pathways. These relationships are most likely the result from changes in dietary composition that affect not only enteric CH4 production, but also the profile of volatile and non-volatile metabolites in milk. Overall, the results indicate that both volatile and non-volatile metabolites in milk might provide useful information and increase our understanding of CH4 emission of dairy cows. However, the development of CH4 prediction models revealed that both volatile and non-volatile metabolites in milk hold little potential to predict CH4 emissions despite the significant relationships found between individual non-volatile metabolites and CH4 emissions. Additionally, combining MFA with milk volatile metabolites and non-volatile metabolites does not improve the CH4 prediction potential relative to MFA alone. Hence, it is concluded that it is not worthwhile to determine the volatile and non-volatile metabolites in milk in order to estimate CH4 emission of dairy cows.

    Overall, in comparison with FTIR, volatile and non-volatile metabolites, the MFA are the most accurate and precise proxy in milk for CH4 emission of dairy cows. However, most of MFA-based models to predict CH4 emission tend to be accurate only for the production system and the environmental conditions under which they were developed. In Chapter 8 it was demonstrated that previously developed MFA-based prediction equations did not predict CH4 emission satisfactory of dairy cows with different DGAT1 genotypes or fed diets with or without linseed oil. Therefore, the greatest shortcoming today of MFA-based CH4 prediction models is their lack of robustness. Additionally, MFA have restricted practical application, meaning that most MFA retained in the current CH4 prediction models cannot be determined routinely because of the use of gas chromatography. The MFA that can be determined with the use of infrared spectroscopy are however no promising predictors for CH4 emission. Furthermore, MFA have only a moderate CH4 prediction potential. This together suggests that it might not be the best option to focus in the future on MFA alone as a proxy for CH4 emission of dairy cows.

    The FTIR technique has a low to moderate CH4 prediction potential. However, FTIR has a great potential for practical high throughput application, facilitating repeated measurements of the same cow potentially reducing random noise. Results of this thesis also demonstrated that FTIR spectra do not have the potential to detect differences in CH4 emission between diets which are, in terms of forage level and quality, commonly fed in practice. Moreover, the robustness of FTIR spectra is currently unknown. Hence, it remains to be investigated whether FTIR spectra can predict CH4 emissions from dairy cows housed under different conditions from those under which the FTIR-based prediction equations were developed. It is therefore concluded that the accuracy and precision to predict CH4 emission using FTIR needs to increase, and the capacity of FTIR to evaluate the differences in CH4 emission between dairy cows and different types of diets needs to improve, in order to actually be a valuable proxy for CH4 emission of dairy cows.

    Lactic acid fermentation of human excreta for agricultural application
    Andreev, Nadejda - \ 2017
    Wageningen University. Promotor(en): P.N.L. Lens, co-promotor(en): B. Boincean; M. Ronteltap. - Leiden : CRC Press/Balkema - ISBN 9781138049895 - 207
    lactic acid - manure fermentation - fermentation - fertilizers - human faeces - biochar - composting - melkzuur - mestvergisting - fermentatie - kunstmeststoffen - mensenfeces - biochar - compostering

    Human excreta is a valuable fertilizer for improving soil quality and crop productivity, with a potential to replace or complement the mineral fertilizers. The main challenges related to human excreta regarding agricultural applications are microbial contamination risks, loss of nutrients, and odor issues. Fertilization by lacto-fermented faeces supplemented by biochar has benefits such as improved soil bulk density, nitrate and potassium concentrations as well as the yield and yield components of corn, compared to untreated, simple stored faeces, urine, cattle manure, and unfertilized controls. Even though the mineral fertilizer produced corn with significantly higher height and leaf length, it did not add significantly higher yields than lacto-fermented faeces supplemented by biochar. A faeces treatment process by combined lacto-fermentation with thermophilic composting and biochar supplementation had better reduction of coliforms, Escherichia coli, Enterococcus faecalis and Clostridium perfringens, and higher germination of radish and growth of tomatoes than combined lacto-fermentation with vermicomposting. Urine lacto-fermentation contributed to a pH reduction below 4, a decrease in the ammonium concentration and odor strength, as well as an increase in the germination rates compared to untreated stored urine. The results of this study provide important information that can set the basis for scaling up a sustainable technology for the treatment of source separated human excreta while improving its potential for resource recovery.

    Effect Molares® op biogas opbrengst bij co-vergisting
    Durksz, Durk - \ 2017
    Lelystad : ACRRES - Wageningen UR (Rapport / WPR 738) - 25
    bio-energie - co-vergisting - biogas - fermentatie - installatieontwerp - voorbehandeling - malen - gasproductie - bioenergy - co-fermentation - biogas - fermentation - plant design - pretreatment - grinding - gas production
    Belo Molares presentation film English
    Durksz, Durk - \ 2017
    pretreatment - biomass - fermentation - gas production - machines - biobased economy
    Microbial chain elongation based on methanol
    Chen, Wei-Shan - \ 2017
    Wageningen University. Promotor(en): C.J.N. Buisman; C. Kroeze, co-promotor(en): D.P.B.T.B. Strik. - Wageningen : Wageningen University - ISBN 9789463431989 - 201
    feedstocks - renewable resources - organic wastes - waste utilization - fermentation - methanol - industriële grondstoffen - vervangbare hulpbronnen - organisch afval - afvalhergebruik - fermentatie - methanol

    Our society relies heavily on fossil resources to fulfill our energy and commodity demands and this dependence has led to negative economic, environmental and societal consequences. The re-generation rate of fossil resources is much slower than their consumption rate, making these resources a non-renewable feedstock for the supply of energy and goods to our society. Moreover, the rapid consumption of fossil resources releases the carbon sequestrated in the last few million years in a much shorter time span, which contributes to the carbon dioxide (CO2) concentration increase in the atmosphere and potentially global warming. The geographically-uneven distribution of fossil resources also induces social insecurities and political conflicts. An alternative feedstock is necessary for energy and goods supply to our society, and such alternative feedstock should be renewable, economically sustainable, environmentally sound and geographically wide-spread,.

    Organic waste is an emerging and promising alternative feedstock. The production of organic waste is inevitable, occurs in large quantities and is geographically wide-spread, especially the so-called “mixed organic waste,” e.g. organic fraction of municipal solid waste (OFMSW) and food processing waste. Mixed organic waste contains a large quantity of carbon materials that can be valorised into energy carriers and commodities. However, the extremely heterogeneous composition and the relatively high water content of mixed organic waste make its valorisation via the current waste management methods (e.g. incineration, composting and anaerobic digestion) less efficient and not economically attractive. Given this context, a novel bioprocess based on a mixed culture fermentation, i.e. microbial chain elongation, was developed to promote the valorisation of mixed organic waste. In microbial chain elongation, the diverse, complex organic matter in mixed organic waste are homogenised via hydrolysis and bacterial acidification into basic building blocks; like short chain fatty acids (SCFAs), CO2 and hydrogen (H2). After the homogenisation, energy-rich co-substrates like ethanol are added to these basic building blocks to synthesise medium chain fatty acids (MCFAs) via a mixed culture fermentation. MCFAs are organic compounds with a higher economic value and a higher energy content. Microbial chain elongation can be operated under a non-sterile condition, which makes it applicable to valorise mixed organic waste where diverse microorganisms exist. Caproate is the most dominant product in the microbial chain elongation of mixed organic waste and ethanol, which can be produced at a high rate and selectivity. Caproate has a higher economic value, a lower solubility in water and an interesting market potential. Thus, caproic acid production from mixed organic waste and ethanol via microbial chain elongation is currently undergoing up-scaling and commercialisation.

    Many studies were done to improve the process of caproate production via microbial chain elongation to make it of industrial interest. The on-going commercialisation of microbial chain elongation also supports the economic feasibility. However, until now, no study addressed the environmental sustainability of microbial chain elongation. Chapter 2 of this thesis took the first attempt in analysing the life-cycle environmental impacts of caproic acid production from organic waste via microbial chain elongation, based on the literature and existing business case. The use of ethanol as a co-substrate (i.e. the electron donor) was shown to be the largest cause the environmental impact. This was found in in all assessed cases and all impact categories studied, and regardless of the feedstocks from which ethanol was produced. An alternative for ethanol as electron donor in microbial chain elongation is, therefore, an effective way to improve the environmental sustainability of microbial chain elongation.

    In Chapter 3, we investigated the use of methanol as an alternative electron donor in microbial chain elongation, i.e. methanol chain elongation, for butyrate and caproate production. Methanol chain elongation was previously demonstrated using a pure culture, but never with a mixed culture. To employ organic waste as feedstock, the feasibility of applying methanol chain elongation in an open mixed culture condition needs to be investigated. In Chapter 3, it was demonstrated in a batch incubation that methanol chain elongation could occur with a mixed culture, where butyrate was the dominant product (4.2 g/L). Caproate production via methanol chain elongation was also demonstrated, though only in a low concentration (0.1 g/L). In a continuous reactor operation, continuous butyrate production (1.5 g/L.day) was achieved via microbial chain elongation of acetate and methanol. However, caproate was not observed in the continuous methanol chain elongation. Interestingly, microorganisms that can perform methanol chain elongation were likely present in the inoculum taken from a previous ethanol chain elongation reactor without any methanol supplement.

    In Chapter 4, the use of methanol chain elongation to synthesise a novel product, i.e. isobutyrate, was proposed and investigated. Methanol chain elongation was found to continuously produce butyrate as the main metabolite, the accumulation of which was found to trigger isobutyrate formation in several previous methanogenic anaerobic digestion studies. It was, therefore, hypothesised that by elevating the butyrate concentration in the medium, methanol chain elongation might be able to produce isobutyrate as another metabolite. The result showed that isobutyrate could be produced as the main product, up to 6.2 g/L, when using acidified supermarket food waste and methanol as the substrate. A continuous methanol chain elongation using synthetic medium was also performed, which achieved a production rate of 2.0 g/L.day over five hydraulic retention times. Moreover, the production of isovalerate was also observed. Isobutyrate has a much larger market potential than caproate, though its production relies wholly on fossil-based feedstock. Isobutyrate biosynthesis was demonstrated in previous studies, but was only achieved using metabolically engineered microorganisms as the biocatalyst and glucose as the substrate. Methanol chain elongation, in contrast, could employ derivatives from organic waste as the substrates and a self-regenerating mixed culture biocatalyst for producing isobutyrate. Moreover, methanol chain elongation may be integrated into the current microbial chain elongation production facility without a significant infrastructure retrofit. All these advantages make methanol chain elongation an interesting and promising isobutyrate production process. The relatively large market potential of isobutyrate promotes the application of chain elongation and the use of organic waste for value-added chemical production.

    In Chapter 5, isobutyrate production was integrated with the caproate production via microbial chain elongation, by concurrently feeding both methanol and ethanol to a mixed culture. The result from Chapter 3 supports the possibility of coexistence of ethanol and methanol chain elongation microorganisms in the same microbiome. In Chapter 4, the possible concurrence of methanol and ethanol chain elongation was also observed. Based on these observations, we hypothesised that methanol and ethanol chain elongation could be integrated to simultaneously produce caproate and isobutyrate. The result showed that such integration was possible when a stable pH was maintained. When pH was controlled between 6.2 – 6.5 and butyrate was supplied in the medium, caproate and isobutyrate could be produced simultaneously. Additionally, increasing the ethanol feeding rate promoted the chain elongation of butyrate to caproate via ethanol chain elongation. The outcome of this chapter demonstrated the possibility of producing two valuable products in a single reactor with a mixed culture which, coupled with further process improvement, may be of industrial interest.

    In Chapter 6, we reflected on the caproate production performance of methanol chain elongation, in comparison with other electron donors used in microbial chain elongation, i.e. ethanol and lactate. Furthermore, we also reflected on the isobutyrate production via methanol chain elongation, in comparison with other emerging products in microbial chain elongation. These reflections could serve as a benchmark for methanol chain elongation as a waste management strategy. Based on this benchmarking, we proposed that methanol chain elongation is a promising bioprocess for isobutyrate production but not for caproate production. A potential strategy for improving the isobutyrate production via methanol chain elongation was proposed and discussed. The outcomes of this thesis may contribute to future application and assessments of microbial chain elongation in waste management. It may fuel discussion on how to further promote microbial chain elongation for a more sustainable waste management.

    Leaf phenolics and seaweed tannins : analysis, enzymatic oxidation and non-covalent protein binding
    Vissers, Anne M. - \ 2017
    Wageningen University. Promotor(en): H. Gruppen; W.H. Hendriks, co-promotor(en): J.P. Vincken. - Wageningen : Wageningen University - ISBN 9789463432023 - 154
    phenols - leaves - seaweeds - tannins - beta vulgaris - laminaria - proteins - catechol oxidase - nuclear magnetic resonance spectroscopy - in vitro - mass spectrometry - browning - fermentation - animal feeding - fenolen - bladeren - zeewieren - tanninen - beta vulgaris - laminaria - eiwitten - catechol oxidase - kernmagnetische resonantiespectroscopie - in vitro - massaspectrometrie - bruinkleuring - fermentatie - diervoedering

    Upon extraction of proteins from sugar beet leaves (Beta vulgaris L.) and oarweed (Laminaria digitata) for animal food and feed purposes, endogenous phenolics and proteins can interact with each other, which might affect the protein’s applicability. Sugar beet leaf proteins might become covalently modified by phenolics through polyphenol oxidase (PPO) activity. Oligomeric phenolics from seaweed (so-called phlorotannins (PhT)) might bind non-covalently to protein. The first aim of this thesis was to study factors involved in protein modification by phenolics. The second aim was to investigate the effect of PhT supplementation to feed on in vitro ruminal fermentation.

    Besides PPO activity and the amount of low molecular weight phenolic substrates present, brown colour formation in sugar beet leaves was dependent on the amount of phenolics, which do not serve as a substrate of PPO. These non-substrate phenolics can engage in browning reactions by oxidative coupling and subsequent coupled oxidation of the products formed. Similar reactions might also be involved in covalent protein modification by phenolics, and therewith protein properties.
    High molecular weight PhT from L. digitata could potentially modify protein properties by non‑covalent interactions. L. digitata contained PhT with subunits mainly connected via C‑O-C linkages, as determined using NMR spectroscopy. Further mass spectrometric analysis revealed the presence of a wide range of oligomers with degrees of polymerisation between 3 and 27. The interaction between PhT and proteins (b-casein and bovine serum albumin) was studied using model systems with different pH values, representing the various environments throughout the ruminants digestive tract. Phlorotannins bound to protein independent of pH, and broadened the pH range of protein precipitation from 0.5 to ~1.5 pH unit around the protein’s pI. At the pH of the abomasum of 2-3, the proteins re-solubilised again, presumably by increase in their net charge. Due to their ability to form water insoluble complexes, PhT could improve ruminal fermentation in vitro in a dose dependent manner, resulting in lower methane production and ammonia (NH3) concentration. The decreased NH3 concentration reflected decreased dietary protein breakdown in the rumen, which is considered a nutritional and environmental benefit.

    Optimal use of biogas from waste streams : an assessment of the potential of biogas from digestion in the EU beyond 2020
    Kampman, Bettina ; Leguijt, Cor ; Scholten, Thijs ; Tallat-Kelpsaite, Jurga ; Brückmann, Robert ; Maroulis, Georgios ; Lesschen, Jan Peter ; Meesters, Koen ; Sikirica, Natasa ; Elbersen, Berien - \ 2017
    Luxembourg : European Commission - 158
    biogas - gas production - fermentation - assessment - production possibilities - residual streams - european union - biobased economy - biogas - gasproductie - fermentatie - beoordeling - productiemogelijkheden - reststromen - europese unie - biobased economy
    As the European Commission is working on the further development and concretisation of the post-2020 climate and energy policies, this study was commissioned to zoom in on the potential role, cost and benefits of biogas, and to assess the key barriers and drivers of biogas deployment in the EU. An important question to address was what policies at both EU and Member State level can best contribute to the effective and efficient growth of biogas deployment in the EU. The study focussed on biogas production by digestion processes of local waste streams, i.e. on biogas production from sewage sludge, landfill gas and from suitable organic waste streams from agriculture, the food industry and households.
    Biogas production and digestate utilisation from agricultural residues : deliverable nº: 6.2.1
    Corre, W.J. ; Conijn, J.G. - \ 2016
    HYSOL project - 39
    renewable energy - anaerobic digestion - biogas - crop residues - agricultural wastes - sustainable energy - electricity supplies - innovations - biobased economy - fermentation - digestate - hernieuwbare energie - anaërobe afbraak - biogas - oogstresten - agrarische afvalstoffen - duurzame energie - elektriciteitsvoorzieningen - innovaties - biobased economy - fermentatie - digestaat
    The HYSOL project aims at hybridisation of concentrated solar power with a gas turbine in order to guarantee a stable and reliable electricity supply, based on renewable energy. The production of fully renewable electricity in a Hybrid Concentrated Solar Power (HCSP) plant includes the use of renewable gas. In task 6.2 of the HYSOL project research into the possibilities of sustainable biogas production from agricultural residues by anaerobic digestion has been performed. In this report results are described of part of this research focussing on potential biogas production and digestate production and utilisation from animal manure and crop residues.
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